A true fitness buff's work is never over. After all, graduating to the next level of athletic achievement means increasing the difficulty of every workout to keep your muscles challenged, including building the amount of weight you lift. But how do you know when the time is right to set aside those five-pound dumbbells in favor of heftier seven-pound kettlebells? According to founder of Surf Yoga Beerand Senior SoulCycle Instructor Mantas Zvinas, there are a few key clues to look out for as you make your way to Olympian status. Read on to discover the signs that mean you're ready to take the next step in your fitness routine.

1. You Never Run Out of Breath

According to Zvinas, the simplest sign that it's time to challenge your body is a lack of anaerobic activity. "When teaching BootYcamp or SoulCycle classes, I ask my students to always look for moments of losing the breath, pushing to failure and knowing if you have more to give," Zvinas reveals. "If you don't hit any of those moments, it is a good sign that it's time to step it up."

2. The Type Workout You Do Hasn't Changed in Years

If you've been going to the same Spin class for years or only using five-pound weights, it may be time to shake things up. While Zvinas recommends his own SYB BootYcamp as an exciting new challenge for those in a workout rut, the trainer states that any new class that works different muscles with different weights will provide results.

"Look for movements you don't do regularly to keep yourself engaged," Zvinas shares. "For example, at my BootYcamp classes, we work on resting in a primal squat, something we grow out of in Western culture, so most people have trouble with their knees and ankle mobility, but that is exactly why we do it in the first place — to improve those areas."

3. You Haven't "Failed" Yet

When it comes to demanding workouts, failure is an option — but not in the way you may think. "To lift heavier, you want to push to failure with heavier weights and less reps — this is where muscle will tear in the correct way and rebuild stronger if you rest and recover correctly," Zvinas shares. In simpler terms, continuing to lift the same light weights for years won't help you build the physique you seek. According to Zvinas, it's better to complete only a few reps with a heavy set of weights than 20 reps with weights that are far below your capability level.

However, Zvinas cautions that muscle fatigue and pain shouldn't be confused when testing out more substantial weights. "I've pushed my body through pain because of a stubborn mind, and the result was a torn meniscus," Zvinas shares. "Yet, of course, to take your body to the next level, you have to have the right mindset. So my best advice is to be listening to the body with 100 percent of your attention and never ignore even small pains."

If you sense that your weights are causing more discomfort than the dull ache that occasionally accompanies a tough workout, stop lifting immediately and consult with a licensed fitness expert to determine if you need to take a step back.

4. Your Brain Is Telling You to Challenge Yourself

Physical signs aren't the only indicators that it's time to amp up your fitness routine. "The time to progress, to go harder, faster, and longer, is always going to be one that will require you to listen to your body and mind in balance," Zvinas says. If you're bored with your current workout or it's leisurely enough that your mind frequently wanders away from the task at hand, it's time to jump into a more difficult regimen.

If the question of increasing the amount of weight you lift has crossed your mind, it's likely time to make the commitment to a more exacting regimen. As with any tweak to your fitness regimen, be sure to speak with an expert before diving in. Once you have your plan in place, get ready for your fittest year yet!